What is enamel?
Enamel is a layer of glass fired to metal. It has been used throughout the centuries for very many different purposes and is a very durable material. The enamel is available in very many different and rich colours. The material is not affected by exposure to light and the atmosphere.
Borate and fluoride glass, fairly soft varieties of glass, form the basis of enamel. Coloured metal oxides, which may affect the transparency, are added to the glass substance. Depending on these additives enamels may be opaque, transparent or opalescent.
Enamel can be fired onto red copper, silver, gold, platinum, aluminium and stainless steel. Each metal requires enamel that has been specially adapted to the metal: it should expand and contract upon heating and cooling in just the same way as the underlying metal, otherwise it will crack and chip off upon cooling after firing. Silversmiths use silver, gold or platinum, others usually fire onto copper.
First the metal is thoroughly cleaned and superficial oxides are removed by sanding, or by exposure to an acid solution (a process called pickling). The enamel powder is then applied to the metal with a brush, by dusting or spraying, depending on the shape and nature of the object. Subsequently the metal is made to adhere by firing it (in the kiln, or with a torch) at a temperature that is appropriate to the particular enamel used (it varies between 690 en 880 °C). The enamel melts and is thus made to adhere to the metal surface.
There are many enameling techniques. We will only very briefly discuss the cloisonné, champlevé plique à jour and grisaille techniques. You will find many examples of enamel panels and of three-dimensional work, occasionally combined to adorn figures in clay, on this website.
The cloisonné technique has been with us since the 5th century BC. In cloisonné enameling the design is made out of thin and flat silver, golden or copper wires. These are arranged in such a manner - on a previously prepared base - that they fence off fields or cells (cloisons) which are subsequently filled with enamel powder. Each colour of enamel is therefore enclosed in its own cell. In early days the meteal wires were needed mostly to keep the enameled areas together. There is no need for that anymore, but the technique is still frequently used by many artists because it allows them to make often stunningly beautiful pieces. The procedure, briefly, is as follows:
- Bend flat and thin wires (copper, silver or gold) into a closed shape. Use each element to form the total design, e.g. a flower with stem and leaves.
- Anneal the metal, i.e. heat the wires to remove tension that arises from changing their shape due to which the metal may have become stiff and brittle.
- See to it that each of the elements that you have formed can ly in perfect contact with the base.
- Clean the metal base thoroughly.
Apply enamel flux (a transparent enamel) to the base; it should be very wet so that a thin and even layer can be formed.
- Use fine tweezers to transfer the wires to their correct place in the enamel flux until the design has been completely transferred.
- Dry the enamel and fire it in the kiln so that it just starts melting and the surface becomes smooth and flat.
- Remove the piece from the kiln on a fireproof material and immediately press the wires down with e.g. a flat spatula to ensure good contact with the enamel.
- Fill each of the cloisons with enamel powder, carefully washed with distilled water and still wet.
After drying, fire it in the kiln.
- As the enamel melts small particles join and move closer together, so that it compacts.
- Therefore lay in additional enamel in each of the cloisons, fire again after drying, and repeat this process as often as required to fill the cloisons evenly and to the top. At each stage one should very carefully prevent coloured enamel particles from falling into a neighbouring cloison.
- Finally the surface needs to be sanded down and polished. To restore the gloss a final, brief firing is required.
Many pieces will need 10 or more firings. The cloisonné technique calls for patience, dedication, a sure touch, experience, and working carefully in a very clean environment.
As in the case of émail cloisonné this technique is old and frequently applied, particularly after the 11th and 12th century. The enamel is applied in fields recessed in the metal. The revival of the technique may have to do with the success of émail cloisonné, where fields are delineated (cloisons) by thin metal strips and subsequently filled with enamel. At the climax of the Byzantine period (9th-12th century AD) this technique was applied on thin gold plaques, leading to beautiful pieces of art. This Byzantine art could not be matched in European workshops, in part due to lack of gold. Copper and bronze could not be used to replace gold. That is why artists in the Rhine and Meuse valleys started to imitate closions by cutting recesses in the metal with various tools.
Using gravers, or nowadays by etching, recesses are formed in the metal, separated by thin strips of metal (as in the cloisonné technique) the width of which one can vary, and subsequently filled with enamel. Since the enamel compacts after each firing, the fields need to refilled and the object refired. After maybe 10 firings the surface is sanded level and polished; one can also restore the shiny gloss of enamel by a final brief firing. In the middle ages the exposed copper or bronze was subsequently guilded.
Carving out the recesses is a laborious, difficult and time-consuming, and it takes great expertise to obtain a thin separating wall. Etching is also time-consuming and not without health risks if chemicals are used. We have therefore developed a technique to cast champlevé objects in silver, ready for enameling. One of the advantages is that a design can easily be flipped, enlarged or downscaled. On the right is an example of émail champlevé objects that have been thus made and used in a necklace. Details of the technique have been published in“Glass on Metal”, but the details are also available on this website under special techniques.
|A beautiful example of plique à jour in gold, made by Fedor Rückert, the goldsmith and master enameller in the workshop of the famous Peter Carl Fabergé. The brooch with bezel-set precious stones is 47 mm wide.|
Unlike other techniques of enameling, plique à jour enamel is made without a metal base. Instead, thin gold or silver wires are soldered, or a suitable object is obtained by sawing out cells from a metal plaque or alternatively by (photo-)etching, creating a pierced metal framework with small bottomless cloisons (see the example in the picture on the right). These cloisons are then filled with ename and fired, with suitable support. Almost invariably transparent enamels are used, so that you can see through it, looking like a miniature stained-glass window. Indeed plique à jour loosely translates as 'braid, or window, that lets in daylight': plique derives from the Latin plicare and means to bend or fold.
The plique à jour technique is most frequently applied in jewelry. This enameling technique, in addition to patience and dedication, requires great professional skill of both the silversmith and enamelist, and the ability to accept failure and start again. All soldering, including that of bezels and findings, needs to be fully finished prior to firing the enamel. The enamel is most often prevented from leaking away in the kiln by supporting it with mica, titanium or other material that does not adhere.
Towards the end of the fifteenth century the émail peint (painted enamel) technique was developed in Limoges. This entails painting a liquid mixture of enamel on a metal surface that has been previously covered with an enamel base. A number of artists used this technique to great perfection and made the most exquisite pieces of art, such as portraits and enameled watches. Painted enamel objects are almost invariably miniatures. The most famous enamel painter was Leonard Limosin (1505 - 1574).
The grisaille technique was also developed in Limoges as a descendant of the enamel paint technique. Not only was it suitable for painting portraits, it could also be used to depict other scenes, such as in the example on the right. The usual procedure is as follows.
- First the metal base (usually red copper) is covered with dark-brown, blackish blue or black enamel.
- After firing the entire surface, or only part of it, is covered with wet, white enamel. After drying a scribe or similar instrument is used to draw the motifs in the white layer.
- Th enamel powder is then removed from both the perimeter of the motifs and the background, so that the motifs stand out as white 'silhouettes' on a dark background.
- This enamel layer is subsequently gently fired after drying. As the dark background shines through, the motifs now appear greyish on a black background.
- One then repeatedly re-applies thin layers of enamel over (part of) the grey motif and fires after each new layer has dried. Thus one can create any shade from dark grey to white.
This process leads to a very expressive motif with light and shadow. The thicker the layer, the whiter the enamel and the more pronounced the relief.
- Exposure to the atmosphere and to light do not affect enamel, unlike paintings. However when enamel is placed outdoors, acid rain might in the long run turn the surface dull as acids work as an etchant.
- The surface can be cleaned with household detergents. However, never use acid solutions, as these will etch the surface which becomes dull, and you will not be able to remedy this.
- The surface can be easily scratched. Never try to remove scratches and dull spots by polishing them, as this will turn the surface dull.
- Avoid applying pressure to the enamel piece: the thin layer is quite fragile and when it cracks this can in an emergency only be remedied by refiring; this has to be done with little delay, before dirt has accumulated in the cracks. Even though the enamel piece has been made with the greatest care one cannot completely exclude that cracks may occasionally appear after a few months due to tension between the metal base and the enamel surface.
- If enamel is applied to silver, such as in silver jewelry, you can clean the silver in the usual way. However, do not use any solution to which an acid has been added.